Friday, August 24, 2012


The firefly plays a special role in Japanese culture. It is called hotaru (蛍, ほたる) and we researchers know it from the expression 蛍雪 (けいせつ), or firefly-writing, which refers to diligence in studying (i.e., continue to study even in such poor light as offered by a firefly). For more wordly people, the firefly is the symbol of passionate love.

At least from the 24 April 1185 battle of Dan-no-ura, where the Genji under Minamoto no Yoshitsune, defeated the Heike (Taira), if not from earlier, it is believed that when soldiers are killed in battle, their souls are transformed into fireflies. Therefore, in Japan the view of hotaru is very sentimental and patriotic.

Today the life of scientists is more peaceful, as researchers are no longer killed like Goethe's Faustus when his grant was up or Giordano Bruno when he came up with the mathematical concept of infinity (see glad not to be on the stake), so we can be cheerful when we see fireflies.

I remember when we moved to Lugano, at the city's border, consisting mostly of untended fields. The place did not even have a name yet, it was just the far end of Besso, or Lugano 3, as the postal system prosaically called it with the introduction of zip codes. As kids we only had to run away from the apartment buildings for a few minutes to be in a completely dark environment devoid of any light pollution. The black sky was dotted with infinite stars, but in summer, towards Cortivallo and the lake of Muzzano, we were immersed in a cloud of fireflies. It was a magic experience.

Of course, today as color scientists we are more interested in the spectrum of the firefly. Entomology teaches us that males and females are anatomically different, with the latter having two lateral light sources and the former three adjacent light sources. This means that we have to measure the sexes independently. How can we achieve that?

In his recent paper in Atti della Fondazione Giorgio Ronchi, volume LXVII (2012), number 3, pages 455–458, Paolo Stefanini reports how he accomplished it.

Firefly spectrum, male

The males normally cruise above the fields, while the females are hidden in the grass. When the females want to mate, the crawl to the apex of the grass leaves and wait. A males ready to mate flashes his light and a female flashes back, then they go at it. Therefore, Stafanini first measured the males, then he built a male decoy using LEDs. The decoy allowed him to beat the females out of the bushes, so he could measure them too.

Sunday, August 12, 2012

La tienda de las curiosidades sobre el color

Gladstone famously asserted Homer—and in fact all Ancient Greeks—were color blind because Homer's works never mentioned a color. I do not know what Gladstone was reading in school, but I remember reading Homer's vivid descriptions of sunrises and sunsets, not to mention the descriptions of light at sea, for example when Odysseus tried to withstand the song of the sirens.

This demonstrates the need to teach the perception of color: if we cannot express it, it does not exist. Today, the world is much more colorful, so it has become an easier task. I remember when I was a kid and the world was much more monochromatic: cars were either black or white, and most clothes were grey. In elementary school, we boys had to wear a black smock, while the girls wore a white smock. Next door from our apartment building, Pasticceria Ceroni had the first TV in Bellinzona, and it was black and white. Later, when color TV came on the market, it was so expensive, that kids used to brag by exclaiming: "my dad makes more money than yours, we have a color TV." Meanwhile my family was so poor that even our rainbows were just in black and white…

Despite all the color stimulation everybody can enjoy today, it still must be sorted out and explained, otherwise kids cannot enjoy the rainbows in color. April 27, Mark Fairchild and Manuel Melgosa Latorre presented a new book edited by the Editorial Universidad de Granada (eug), in collaboration with the Parque de las Ciencias that makes a wonderful contribution toward this task: “La tienda de las curiosidades sobre el color.”

El libro “La tienda de las curiosidades sobre el color” da respuesta a 64 preguntas didácticas sobre el color: ¿Cuántos colores hay en el mundo?, ¿qué es el color?, ¿cuál es el mejor color para unas gafas de sol?, ¿por qué el cielo es azul?, ¿puede un perro ver el color lo mismo que yo?, ¿por qué tienen las flores distintos colores?, ¿por qué no podemos ver los colores de noche?, ¿por qué mis fotos no tienen los mismos colores que las escenas originales?

Estos son algunos de los interrogantes que el libro desvela. Las preguntas están ordenadas en 8 módulos (luz, objetos, ojos, etc.), y dentro de cada módulo hay 8 niveles de creciente complejidad, ya que el libro va dirigido tanto a estudiantes de primaria como a estudiantes universitarios, y también a cualquier persona interesada en la ciencia.

The book is also available in English: Explore Mysteries of Color — Discover Why is Color.